Keeping secret the identity of products involved in various kinds of testing while, at the same time, having such product labelled in such a manner that the product (and all its components, if applicable) is readily identifiable when such information is required has been a longstanding problem. This aspect of secrecy in testing is frequently referred to as "blinding."
In order to solve this problem, various types of label blinding techniques have been devised where the area of the label which describes the full contents of the container or package has been covered with a form of removable opaque material. To date, such labels have included: manufactured products that consist of multi-laminants with a pasted pocket using carbon spot and/or carbonless paper to transfer an image into a secret pouch (like a payroll envelope); products in which the secret information is located inside a sealed-pasted pouch by use of clever folding techniques; overlays using removable pressure-sensitive labels; and products where an alcohol wipe or cotton swab soaked with alcohol would be used to wipe away an alcohol-soluble ink which had been printed over the information about the contents of the package. Techniques have also been used where a base sheet is preprinted with the information about the container's contents and an opaque paper cover is heat-sealed over the information on either a continuous form basis or on an individual label basis using unique heat sealing machinery. Opaque material is sometimes screen printed on a label, but it often peels and cracks and is generally too sensitive to abrasion with this process.
Generally, manufacturing of the labels requires special materials with relatively long production lead times. The blinded label manufacturing processes are slow, do not permit individual labels to be precut, and require considerable labor and manual intervention in two to three production steps.
The security and secrecy associated with these various types of blinding labels are reduced when the information on them is applied using computer-driven printing techniques. The printers leave impressions, such as with daisy wheel printers and dot matrix printers, or they deposit ink with ink jet printers or with powdered pigment which is fused onto the paper with a heating element (as with laser printers). When someone is determined to access the blinded information, the surface impressions made by impact printing can be made to reveal the encrypted information. Similarly, laser printed characters are raised above the surface of the paper to which they are adhered. Close observance of these surface deposits and their resultant patterns can effectively decode a hidden message. These problems discourage the use of computer-driven printing techniques, requiring resort to slower and more costly printing techniques.
In certain types of testing where knowledge of the contents of the package is not critical (e.g., comparative testing of laundry detergents), the information about the contents could be simply coded. Pharmaceuticals, however, generally require labels having a complete description of the contents of the container to which they are attached in order to comply with all state and federal laws and regulations. A complete description of the product must be maintained for days in interstate commerce.
There is a need for, and the objects of the invention are to provide, a label and a method to produce that label such that: (a) the label contains the complete description of the contents of the container or package; (b) the blinding process and materials used do not allow the blind to be broken by observing the impressions or surface deposits left by the printer; (c) if someone does attempt to break the blind, evidence of such tampering is readily apparent; (d) the blind may easily be broken when it is appropriate to do so; (e) large quantities of labels meeting these criteria may be produced quickly and cost effectively and with minimal labor requirements; and (f) different configurations of labels and different configurations of the secret areas contained thereon can be easily blinded.